Corrosion-resisting composite metal



Sept. 27, 1949. P. e. CHACE 2,482,898

CORROSION-RESISTING COMPOSITE METAL Original Filed June 23, 1941Patented Sept. 27, 1949 Paul G. chm, Attleboro Falls, Masa, assumitoMetals and Controls Corporation, Attleboro, Mass, a corporation ofMassachusetts Original application June 23, 1941, Serial No.

399,398, now Patent No. 2,368,178, dated January 2, 1945.

Divided and this application November, 11, 1944, Serial No. 563,014

7 Claims. (Cl. 29-1955) This invention relates to composite metalelements and particularly to bimetallic elements which arecorrosion-resisting.

This application is a division of my co-pendmg application, serial No.399,398 filed June 23, 1941,

Patent 2,366,178.

Among the several objects of the-present invention are the provision ofa composite thermost-ating metal which is corrosion-resisting, which hasan improved bond, and which has a long life when operating incorrosion-promoting atmospheres and mediums; the provision of compositethermostatic metal of the class described which has both goodhot-rolling and good cold-rolling properties; and the provision ofcomposite thermostatic metal of the type indicated which is relativelysimple and economical to manufacture. Other objects will be in partobvious and in part pointed out hereinafter.

The invention accordingly comprises the ingredients and combinations ofingredients, the proportions thereof, and features of composition, whichwill be exemplified in the products hereinafter described, and the scopeof the. application of which will be indicated in the following claims.

In the accompanying drawing in which is illustrated one of variouspossible embodiments of the invention, the single figure is arepresentation of a bimetallic element showing a strip of iron chromiumalloy fused throughout its length to a similar strip of copper siliconalloy.

Many of the thermostatic elements commonly in use are subjecttocorrosion when used in the presence of moisture in places such as steamradiators, or water mixing valves, or in other installations wherecorrosion-promoting fluids or atmospheres come in contact with thethermostatic metal. As a result, such elements frequently needreplacing, and inasmuch as corrosion tends to reduce their activity andlife, such corrosion may set up, unknown to the user, dangerousconditions which might result in loss of life or injury. To avoid thiscorrosion of the composite metal element, it has sometimes beencustomary in the past to treat the thermostatic metal surface to make itless subject to corrosion, as by plating it with a corrosion-resistingmaterial, such as cadmium, tin, zinc, lead, or chromium. This, however,has the disadvantage that the plating increases the cost materiallyanddoes not assure satisfactory life for the thermostatic element.Furthermore, such plating is not entirely satisfactory since anelectrovoltaic potential may be set up which produces pitting and eatingaway of the protective metal.

It has sometimes been the practice in the past to make a compositemetallic element from an iron alloy having a high chromium content, andametal alloy having a higher coefllcient of expansion. The metal usedfor the high coeflicient of expansion side has been one of the brasses.The mechanical properties of these brasses have presented manufacturingdiffiulties, which in many instances have prevented the manufacture ofan adequate and satisfactory composite metal. For example, thecold-working properties of brass are so different from those of thechromium iron alloy that it has been diflicult to satisfactorilycoldwork the metal after it has been put together to form a thermostaticbimetal. Moreover, it is highly advantageous in the manufacture ofbimetal to hot-roll the material down from its thick ingot size to anintermediate stage. The brasses are not adapted to this, since theirhot-rolling temperatures differ too much from that of the chromium ironalloy. The manufacture of the brass-chrome iron bimetals has thereforebeen a relatively expensive process compared to the manufacture ofbimetal in accordance with the present invention. The ingot size of thebrasschrome iron bimetals must be kept small because of theaforementioned difficulties and properties.

Where other constituents have been proposed for corrosion-resistingbimetals, it has been found relatively impossible to directly bond themetals together. For this reason, an intermediate solder layer has beenused which has led to two serious disadvantages. First, the use of thesolder layer decreases the corrosion-resisting property of thethermostatic metal due to inferior bonding, and second, the solder layerdecreases the strength of the metal at elevated temperatures, since thesolder bond is relatively weak. Also, solderbonded material is difficultto hot-roll satisfactorily.

By the present invention, it is possible to accomplish a direct bondbetween the metals, and they may be hot-rolled or cold-rolled in thedesired manner. Their manufacture is accordingly economical, and ahighly corrosion-resisting thermostatic metal is obtained.

According to the present invention a thermostatic element is providedwhich is corrosionresisting per se, particularly to air, water andgether over their entire areas by a direct bond,

One of the layers, in the present invention, comprises acorrosion-resisting metal having a low coefficient of expansion. Theother layer comprises a second corrosion-resisting metal having arelatively high coeillcient of expansion.

For the metal having a low coefllcient of expansion a high chromiumcontent stainless iron is employed. The composition of this alloy may beas follows:

Per cent Manganese 0.2-0.6 Carbon 0.01-0.2 Chromium '12-20 Silicon -1.5Copper 0-1.5 Iron Remainder For the high expansion material an alloy ofcopper and silicon is employed. The composition of this alloy may be asfollows:

Per cent Copper 96-99 Silicon 0.5-4 Manganese 0-1 The compositethermostatic metal of which bimetal will be described as an illustrativeembodiment may be formed in any of the customary manners. It ispreferably formed in one of the ways described in my co-penclingapplication, Serial No. 399,398, filed June 23, 1941, Patent 2,366,178,referencev to which is hereby made.

Referring now to the drawing, the single figure illustrates a bimetallicelement composed of the two alloys discussed above. Numeral i representsthe copper silicon alloy while 3 is the iron chromium alloy.

The tensile strength and other mechanical properties of the coppersilicon alloys described are sufiiciently near to the same properties ofthe chrome-iron alloys that the two metals work. well together and maybe easily cold-worked. This makes the manufacture thereof moreeconomical. As a result of obtaining a direct bond between the metalscomprising the present invention, a thermostatic metal having a higherstrength, greater activity, wider usable temperature range, longer lifeand better corrosion-resisting properties than the corrosion-resistingbimetals hitherto known, is obtained. Former metals allegedly designedto have these desirable properties have instead been relatively weak,corrode relatively easily, are more dificult to manufacture, and ingeneral are not satisfactory.

As specific examples of alloys which may be advantageously employed inthe present invention, the following examples are given. They areillustrative only:

Chrome-iron Alloy N0. 1

Per cent Manganese 0.2-0.6 Carbon 0.01-0.2 Chromium 12-20 Silicon .2-1.5Copper .5-1.5 Iron Remainder Chrome-iron Alloy No. 2

Per cent Manganese 0.4 Carbon 0.05 Chromium 16 Silicon 1 Copper 1 IronBalance Attention is directed to my copending applications, Serial Nos.563,013, 563,015 and 563,016, all filed November 11, 1944.

In view of the above it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above alloys, without departingfrom the scope of the invention, it is intended that all mattercontained in the above description shall be interpreted as illustrativeand not in alimiting.' sense.

I claim:

1. A corrosion-resisting thermostatic metal composed of an alloy havingessentially the following composition:

Percent Manganese l 0.2-0.6 Carbon 1 0.01-02 Chromium 12-20 Silicon.2-1.5 Copper 5-1.5 Iron Remainder and an alloy having essentially thefollowing composition:

. Per cent Copper 96-98 Silicon 2-4 the surfaces of said alloys beingfused together at the junction.

2. A corrosion-resisting thermostatic metal composed of an iron alloycontaining: manganese approximately 02-06%, carbon approximately0.01-0.2%, chromium approximately 12-20%, silicon approximately 0.2-1.5%copper approximately 0.1-1.5%, and the balance iron; and a copper alloycontaining: silicon approximately 0.54%, and the balance copper; thesurfaces of said alloys being fused together at the junction.

3. A corrosion-resisting thermostatic metal composed of an alloy havingessentially the following composition:

Per cent Manganese 0.4 Carbon 0.05 Chromium 16 Silicon 1 Copper 1 IronRemainder and an alloy having essentially the following composition:

Percent Copper 96-98 Silicon 2-4 the surfaces oi said alloys being fusedtogether at the junction.

4. A corrosion-resisting thermostatic metal composed of an alloy havingessentially the following composition:

Per cent Manganese 0.4 Carbon 0.05 Chromium 12-16 Silicon 1 Copper 1Iron Remainder and an alloy having essentially the followingcomposition:

Per cent Copp r 98-98 Silicon 2-4 the surfaces of said alloys beingfused together at the Junction.

'5. A corrosion-resisting thermostatic. metal composed of an alloyhaving essentially the following composition:

the surfaces of said alloys being fused together at the junction.

6. A corrosion-resisting thermostatic metal composed of an alloy havingessentially the following composition:

Per cent Manganese 0:4 Carbon 0.05 Chromium 16 Silicon 1 Copper 1 IronRemainder 6 and an alloy having essentially the following composition:

- Per cent Copper 9'? Silicon 3 the surfaces of said alloys being fusedtogether at the junction.

7. A corrosion-resisting thermostatic metal composed of an alloy havingessentially the following composition:

Per cent Manganese 0.4 Carbon 0.05 Chromium 12-16 Silicon 1 Copper r 1Iron Remainder and an alloy having essentially the followingcomposition:

Per cent Copper 97 Silicon. 3

the surfaces of said alloys being fused together at the junction.

PAUL G. CHACE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,650,951 Matthews Nov. 29, 19271,948,121 Matthews Feb. 20, 1934 1,991,438 Wohrman Feb. 19, 19352,075,014 Bassett Mar. 30, 1937 2,087,431 Felld July 20, 1937 OTHERREFERENCES Pages 1000-1002 of The Making, Shaping, and Treating ofSteel, 5th ed., 1940, pub. by Carnegie- Ill. Steel Corp., Pittsburgh,Pa.

